1. Field of the Invention
The present invention relates generally to a duct type single air conditioning system for a multi-zone space, and more particularly, to a barometric bypass damper and a method of adjusting the damper for regulating the air flow and pressure in a variable air quantity control system capable of regulating temperature in each zone independently of each other.
2. Description of the Prior Art
Conventional residential single air conditioning systems (which can provide both heating and cooling i.e. HVAC system) are typically controlled by a single thermostat which controls the unit with the system having fixed diffusers for supplying air to the space. Accordingly, the one set point in the thermostat will cause the temperature in the vicinity of the thermostat to be controlled to the desired level, but in other parts of the residence the temperature can vary widely due to heat load through windows, shading of spaces, heat generated by people or equipment, and various other factors. Thus, certain places in homes require more or less temperature control than others. Upstairs areas have drastically different heating/cooling requirements than downstairs areas or basements. Bedroom areas need temperature control only at certain times of the day or night. Homes with large areas of glass present several problems for maintaining a comfortable temperature. Most residences have areas that are exposed to direct sunlight during certain hours. In both Summer and Winter, those zones require different levels of heating or cooling than other part zones of the home. With a single centrally-located thermostat it is impossible to have optimum temperatures in all zones/rooms at all times.
In a zoned residence, however, individual zones with differing heating/cooling properties and hours of use can be kept at optimum temperatures. One zoning method uses separate heating and cooling units with fixed diffusers to maintain different comfort levels in different parts of the residence. However, each separate system uses its own thermostat which is centrally located in a zone to be maintained by the respective system, but, because the separate units do not function as a whole system, they may over lap in heating and cooling some areas and perform as two independent systems.
To overcome the added installation costs, added expense to operate, and the overlap problems with dual equipment zoned systems, the use of single heating and cooling units with a plurality of motorized dampers can be provided. A single unit zoned system allows different parts of a residence to be controlled at different temperatures at different times by programming a thermostat for controlling dampers in each zone for a desired temperature over a period of time. Although the zoned single HVAC system offers cost savings, greater comfort, and greater flexibility by allowing the homeowner to set different temperatures throughout the house only during times of need or occupancy, these single heating and cooling units with multiple motorized dampers also have some disadvantages. Conventional single heating and cooling zoned systems use a zone control damper system, whereby when the zone control dampers are modulating to a closed position static air pressure builds up or increases in the ducts as the individual dampers modulate closed, thereby increasing the pressure or the air supplied through the ducts to various dampers which remain open.
Prior attempts have been made to resolve the aforementioned problem of static air build-up, as by inserting a bypass damper between the air supply outlet of the HVAC unit and the return air intake of such a unit to cause a recirculation of a quantity of air or an approximation thereof which may have been closed off by zone dampers or the like and to approximate a more uniform air supply pressure to the various zones. In most of the prior art systems, the bypass damper has been controlled by an air pressure sensor or a velocity sensor associated with the air supply outlet of the HVAC unit. Such prior art systems have many shortcomings among which are that the prior art dampers did not function well and sometimes may be closed when they should have been open and the difficulty if not impossibility of locating the prior art sensors within the air supply outlet of the HVAC unit or other location in the main duct system to achieve the predetermined and consistent results desired. Further, the prior art diffuses become noisy when closed and there is no means to adjust the bypass damper to reduce the setpoint pressure to allow more air to be bypassed to eliminate the noisy diffusers.
The bypass control system in accord with this invention alleviates the aforementioned problems in the prior art systems, by providing an improved barometric bypass damper assembly independent of flow, that is a mechanical device which requires no electrical wiring or power and has a curvilinear torque/pressure (position) relation suitable to the simple mechanical controls, while having an adjustment means, independent of gravity, which allows field adjustment of the torque/pressure relation.